First of all thanks for the update..When I was playing with new version I noticed that threads/ropes in pulley joints are applying compressive forces also, but I think that they should be applying tensile forces only.. Hence the force on connecting bodies should be zero when thread slacks(its length becomes smaller than natural length), but in this joint thread does't seem to attain length less than natural length. Expected constraint should be imposed on upper limit only, means whenever length of threads have tendency to attain more length it should apply necessary impulses to maintain length, else no impulses at all. what should i do to get this behaviour.Regards..Mahesh Kurmi

Yes. As of right now the PulleyJoint acts like a fixed length DistanceJoint. So when one rope is shortened the other is elongated. I have added some code to allow a "slack" feature that will be in the next release (this week is my plan):